Objective: To compare the reference values for PEF suggested by other authors in 1963, 1989 and 2001 (for populations in the USA, England and Cuba, respectively) with those obtained from a population sample in the city of São Carlos, Brazil, and to determine whether there is concordance among them. Methods: A total of 243 volunteers (123 females and 120 males; 20-70 years of age) participated in the study. The PEF measurements were performed with the volunteer standing, using a nose clip, by means of a portable peak flow meter. These measurements were compared with the reference values using the Friedman test and Dunn's post-hoc test (p < 0.05). Results: Significant differences were found in all age groups from both genders regarding the values predicted in 1989; the same occurred in the 20-30 and 31-40 age groups (both genders), as well as in the 61-70 age group (females only), regarding those predicted in 2001, as well as in the 20-30 age group (males only) regarding those predicted in 1963. Conclusions: The values predicted in 1963 are appropriate for a population of individuals with the same characteristics as the study sample, except for males in the 20-30 age group. Our study is relevant due to the fact that our sample was larger than that evaluated in the 1963 study. The majority of the values predicted in 1989 and 2001 overestimated the PEF values obtained in our study, proving to be inappropriate for the population studied.

Keywords: Reference values; Respiratory function tests; Airway obstruction; Peak expiratory flow rate.

Objective: To determine whether the quality of life of adolescents with asthma correlates with parameters obtained prior to and after the six-minute step test (6MST); spirometric results after the 6MST; and level of physical activity. Methods: Nineteen adolescents with asthma, ranging from 11-15 years of age, were assessed with spirometry, 6MST, the International Physical Activity Questionnaire (IPAQ), the Pediatric Asthma Quality of Life Questionnaire (PAQLQ), and the 10-point Borg category-ratio scale. Results: Sensation of dyspnea correlated negatively with the total PAQLQ score (r = −0.54) and with the scores of its activity limitation (AL) and symptoms domains (r = −0.64 and r = −0.63, respectively), leg fatigue also correlating negatively with those same domains (r = −0.49 and r = −0.56, respectively). The total IPAQ score correlated with the total PAQLQ score (r = 0.47) and with the PAQLQ AL domain (r = 0.51); IPAQ time spent walking correlated with the PAQLQ symptoms domain (r = 0.45); and IPAQ time spent in vigorous activity correlated with the AL domain (r = 0.50). In the regression analysis, only sensation of dyspnea remained significantly correlated with the total PAQLQ score and the PAQLQ AL domain; leg fatigue remained significantly correlated with the symptoms domain. Conclusions: Higher levels of physical activity indicate better quality of life, as do lower perception of dyspnea and less leg fatigue. The 6MST proved to be a viable option for evaluating exercise capacity in adolescents with asthma, because it reflects the discomfort that asthma causes during activities of daily living.